The eclosion hormone of silkmoths has a number of neurally related effects: (1) it releases the behavior associated with the escape from the pupal cuticle; (2) it "turns-on" adult behavior; and (3) it triggers muscle degeneration in the abdomen. The hormone acts directly on the CNS and its action is mediated through an increase in cyclic AMP. The eclosion hormone will be at least partially purified and characterized. This will possibly allow the production of a radiolabeled hormone that can be used to indicate which neurons in the abdominal CNS bind the hormone. The role of cAMP in the action of the eclosion hormone will be examined. The ability of phosphodiesterase inhibitors to enhance subthreshold doses of the eclosion hormone will be tested. Using immunofluorescence histochemistry, we will determine which neurons show cAMP increases after hormone addition. The pattern of cAMP increases after blockade of chemical synapses should indicate which neurons are probable target cells. Electrophysiological studies will examine the pre-eclosion behavior. Can one localize hormone sensitive neurons that drive the behavior? Is synaptic interaction necessary for the generation of the behavior? Extracellular and intracellular studies of the abdominal motoneurons will be undertaken to determine what changes go on in the neurons to cause them to lose their respective muscles. Light and electron microscopic studies of the motoneurons will also be made to identify possible differences in the neurons before and after eclosion.